session, com_stmt: fetch all rows during EXECUTE command (#42473)

[ti-chi-bot]

This is an automated cherry-pick of #42473

What problem does this PR solve?

Issue Number: close #42424, close #41891

What is changed and how it works?

1. Fetch all rows and store them in the fetchedRows in the ResultSet.
2. Close the result set in EXECUTE command, so we don't need to close it again in the following commands (FETCH, RESET and CLOSE)

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Test with the following a little bigger table:

import java.math.BigDecimal;
import java.sql.*;

public class Example {
    public static void main(String[] args) throws SQLException, InterruptedException, Exception {
        Connection conn = DriverManager.getConnection("jdbc:mysql://127.0.0.1:4000/test?useCursorFetch=true&useServerPrepStmts=true&useSSL=false", "root", "");

        conn.setAutoCommit(false); // must set

        conn.prepareStatement("drop table if exists t").execute();
        conn.prepareStatement("create table t (id int primary key, id_2 int)").execute();

        for (int i = 0; i < 10000; i++) {
            PreparedStatement stmt = conn.prepareStatement("insert into t values (?, ?)");
            stmt.setInt(1, i);
            stmt.setInt(2, i);
            stmt.execute();
        }

        // submit a statement with more arguments:
        PreparedStatement statement1 = conn.prepareStatement("" +
                "select * " +
                "from " +
                "t " +
                "where id > ? and id_2 > ?");
        statement1.setFetchSize(500);
        statement1.setBigDecimal(1, new BigDecimal(2));
        statement1.setBigDecimal(2, new BigDecimal(2));
        ResultSet rs_1 = statement1.executeQuery();

        // submit a statement with less arguments:
        PreparedStatement statement2 = conn.prepareStatement("" +
                "select * " +
                "from " +
                "t " +
                "where (id > ?)");
        statement2.setFetchSize(500);
        statement2.setBigDecimal(1, new BigDecimal(1));
        ResultSet rs_2 = statement2.executeQuery();


        // fetch the result from the first argument
        int iter = 3;
        while (rs_1.next()) {
            int result = rs_1.getInt(1);

            if (result != iter++ ) {
                throw new Exception("");
            }
        }
        System.out.println(iter);
        iter = 2;
        while (rs_2.next()) {
            int result = rs_2.getInt(1);

            if (result != iter++ ) {
                throw new Exception("");
            }
        }
        System.out.println(iter);

        conn.commit();
        statement1.close();
        statement2.close();
        conn.close();
    }
}

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

It stores all rows of a cursor fetch statement locally, while execuing the EXECUTE command, so it will eat up more memory (related with the size of query).

Release note

Previously, TiDB loads data in `FETCH` command with the `cursorFetch` enabled. Now, TiDB will load all data into the memory in `EXECUTE` command. It'll use more memory according to the size of result. And also, TiDB will never report write conflict in `FETCH` command with read-committed isolation level.

[ti-chi-bot]

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[ti-chi-bot]

@ti-chi-bot: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/unit-test	b2821c8	link	true	/test unit-test
idc-jenkins-ci-tidb/check_dev	b2821c8	link	true	/test check-dev
idc-jenkins-ci-tidb/check_dev_2	b2821c8	link	true	/test check-dev2
idc-jenkins-ci-tidb/build	b2821c8	link	true	/test build
idc-jenkins-ci-tidb/mysql-test	b2821c8	link	true	/test mysql-test

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[YangKeao]

I'll submit a cherry-pick manually. Close this one.

[tiancaiamao]

I'll submit a cherry-pick manually. Close this one.

#42602

[ti-chi-bot]

This cherry pick PR is for a release branch and has not yet been approved by release team.
Adding the do-not-merge/cherry-pick-not-approved label.

To merge this cherry pick, it must first be approved by the collaborators.

AFTER it has been approved by collaborators, please ping the release team in a comment to request a cherry pick review.

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